I think going swimming in my spare time I think is great fun and good exercise as well a

问题补充：

I think going swimming in my spare time, I think is great fun and good exercise as well as a useful skill.

A. which

B. as

C. that

D. what

答案：

(答案→)A. which

B. as

C. that

D. what

解析：定语从句考查题。先行词为整个主句之意关系词which在从句中做主语。句意：我认为业余时间游泳是一件有意思的事情既是锻炼又是技能的培养。